Since the days of legacy support are drawing near the end, and the builtin legacy material api support is already on its final legs, I need to start considering to replace all of the legacy MaterialData code with a unified BlockData API more in line with the future. Spigot only offers a builtin BlockData API since MC 1.13. BlockData (or rather, 'IBlockData') is available in NMS since Minecraft 1.8. Before that it was block type ids and block data values. Is there a comprehensive mirror of the Spigot BlockData API/plugin that supports Minecraft 1.8 to 1.12.2 (and 1.13+ as well of course)? If there is not I would probably end up writing an API myself in BKCommonLib. I already have one but it is extremely limited. There is no business logic like changing/reading the state of levers or obtaining the facing of signs.
